Republican presidential candidate, former Massachusetts Gov. Mitt Romney walks back to his vehicle after he briefly watched military jets take off upon his arrival at Des Moines International Airport in Des Moines, Iowa, Friday, Oct. 26, 2012, before heading to a campaign event in Ames, Iowa. (AP Photo/Charles Dharapak)

Republican presidential candidate, former Massachusetts Gov. Mitt Romney walks back to his vehicle after he briefly watched military jets take off upon his arrival at Des Moines International Airport in Des

Republican presidential candidate, former Massachusetts Gov. Mitt Romney gets out of his vehicle before boarding his campaign plane at Toledo Express Airport in Toledo, Ohio, Friday, Oct. 26, 2012, as he

AMES, Iowa - Republican presidential candidate Mitt Romney is calling for "bold changes" to help revive the nation's economy as he outlines a closing economic argument in a speech Friday in Iowa.

Romney did not unveil specific plans in excerpts released before he spoke, but he heaps criticism on President Barack Obama for trying to "distract our attention from the biggest issues to the smallest - from characters on Sesame Street and silly word games to misdirected personal attacks he knows are false."

"This is not the time to double down on the trickle-down government policies that have failed us," Romney says. "It is time for new, bold changes that measure up to the moment that can bring America's families the certainty that the future will be better than the past."

Romney argues that Obama has no proposals to meet "the challenges of the times." He dismisses the president's signature legislative achievement, a health care law, as "his vaunted Obamacare" and says he would instead focus on saving Medicare and Social Security.

"We will create 12 million new jobs in just four years," Romney said, "raise take-home pay, and get the American economy growing at four percent a year-more than double this year's rate. After all the false promises of recovery and all the waiting, we will finally see help for America's middle class."

Romney is focusing on the public's economic concerns heading into the final days of the campaign as polls suggest Americans trust him more than Obama to handle the issue.

But the speech does not answer lingering questions about how specifically he would pay for his tax plan or replace the president's health care law.

Romney also repeats many of his standard campaign themes, including his signature refrain that America can't afford another four years like the last four years, and criticizes the idea of new economic stimulus spending.

"It will not stimulate the private sector any better than did the stimulus of four years ago," Romney says.

Romney was delivering the speech at Kinzler Construction Services, which received several hundred thousand dollars in stimulus funding from the package Obama signed into law shortly after taking office in 2009. Federal data shows the company accepted nearly $650,000 from the Department of Energy and another $39,000 as a subcontractor to help renovate a federal building.

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